The definition of slouch is to move, sit or stand with bad posture, with your shoulders bent forward.(verb)
When you are slumped over on the sofa instead of sitting up straight, this is an example of when you slouch on the sofa.
Slouch is defined as an incompetent person or a lazy, drooping, improper posture.(noun)
See slouch in Webster's New World College Dictionary
Origin: < ? dial. slouk, a lazy fellow < ON slōkr < slōka, to hang down, droop < IE *(s)leug-, var. of base *(s)leu-, to hang limply > slug, sleet
See slouch in American Heritage Dictionary 4
verb slouched, slouch·ing, slouch·es verb, intransitive
Origin: Origin unknown.
Learn more about slouch